The Hydrocracker Unit is the new popular heavy oil conversion unit upgrading low value oil into cleaner, high value fuel products. Many refineries around the world are adding hydrocrackers to address low and ultra low sulfur diesel requirements while providing some flexibility in product yields between gasoline and diesel.
Challenge: One key challenge is properly controlling reactor bed temperatures to get the desired yield, longer catalyst life (less coking), and lower probability of temperature excursion. In order to get good reactor temperature control, the temperature indications need to be working properly and control valves respond to small changes in controller output.
Solution: Emerson provides an advanced process control solution that takes advantage of tight control in the field through the use of Fisher Controls DVC digital positioners on hydrogen quench valves. In addition, the use of Rosemount temperature transmitters 3144P (Dual sensor inputs) and 848T (High Density Measurement) ensure measurements are true. The 3144P’s advanced diagnostics capabilities enable detection of sensor drift, potential thermocouple loop degradation, and enhanced insight into your processes and instrumentation.
Hydrotreaters are the last line of defense in protecting downstream process catalyst. When a hydrotreater is not performing well, poisons introduced downstream can significantly affect product yield, efficiency, and move up the catalyst life replacement date requiring a shutdown earlier than planned.
Challenge: Today’s hydrotreating catalyst are highly active and highly selective. This high performance catalyst requires temperature control loop performance to ensure quality hydrotreating.
Solution: Today’s modern control system, DeltaV, has embedded MPC that is easy, fast, and inexpensive to implement. The use of MPC on simple, but important processes like hydrotreating provide the process control performance required to effectively benefit from highly active catalyst.